Field of the Invention
The present invention relates to a radiographic imaging device and radiographic imaging method that image radiographic images.
Description of the Related Art
In recent years, radiographic imaging devices using radiation detection elements such as flat panel detectors (FPDs), in which an X-ray sensitive layer is disposed on a thin-film transistor (TFT) active matrix substrate and which can directly convert X-ray information into digital data, have been put into practical use. FPDs have advantages compared to conventional imaging plates, such as the user being able to check images instantly and also being able to check moving images, and the use of flat panel detectors continues to spread at a rapid pace. Various types of radiation detection elements have been proposed, such as, for example, the direct-conversion-type, which directly converts radiation into charges using a semiconductor layer and stores the charges, and the indirect-conversion-type, which first converts radiation into light using a scintillator comprising CsI:Tl, GOS (Gd202S:Tb), or the like and then converts the light into charges using a semiconductor layer and stores the charges.
Radiation detection elements have, for example, plural scan lines and plural signal lines that are disposed intersecting one another and pixels that are disposed in a matrix in correspondence to the intersections between the scan lines and the signal lines. The plural scan lines and the plural signal lines are connected to external circuits (e.g., amplifier integrated circuits (ICs) and gate ICs) at the peripheral portions of the radiation detection element.
In order to increase the resolution of FPDs, reducing the size of the pixels of the radiation detection element is effective. Particularly in direct-conversion-type radiation detection elements utilizing Se or the like, pixel size directly contributes to an improvement in resolution, so various types of radiation detection elements that improve picture quality by increasing definition have been proposed. For example, in FPDs for mammography, that has an emphasis on resolution, products with a small pixel size have been proposed.
However, in a case where the pixel size has been reduced, the quantity of charges that can be collected in proportion thereto decreases and, as a result, sensitivity (S/N) drops. For this reason, even if the resolution improves, this ends up causing the problem that the overall image quality detective quantum efficiency (DQE; which is proportional to {S/N×1/resolution}) drops.
Meanwhile, in order to realize a balance between resolution and improving sensitivity, a detection device in which pixels are arranged offset by half a pitch in the X and Y directions and which performs inter-pixel interpolation processing on the basis of generated image information has been proposed (see Japanese Patent Application Laid-Open (JP-A) No. 2003-255049). Further, an X-ray detection device that uses hexagonal shaped pixels to improve the efficiency with which light is utilized has been proposed (e.g., see JP-A No. 2006-29839).
For example, a length (maximum diagonal length) d1max of the longest diagonal of a regular hexagonal shape and an surface area S1 of the regular hexagonal shape have the following relationship.d1max=√(8/3√/3)×S1≈√1.54×S1
In a case where the surface area S1 of the rectangular hexagon=10,000 μm2, a comparison between a regular hexagonal pixel and a square pixel that have the same pixel area shows the following (see also FIG. 8A and FIG. 8B).
Square: length a1 of one side=100 μm, surface area S1=10,000 μm2, maximum diagonal length d1max=141 μm
Regular hexagonal shape: length a1 of one side=107 μm; surface area S1=10,000 μm2; maximum diagonal length d1max=123.5 μm
Consequently, given the same pixel area, the diagonal length d1max can be reduced by 12% in the case of the regular hexagonal shape compared to the square.
A radiographic image detected using the detection devices described in JP-A No. 2003-255049 and JP-A No. 2006-29839, which use hexagonal shaped pixels, becomes an image in which the pixels are arrayed in a honeycomb pattern. Meanwhile, many output devices such as printers and monitors are configured with the assumption that they will handle images in which the pixels are arrayed in a square grid pattern. For this reason, in order to make the detected radiographic image compatible with these output devices, it is necessary to perform pixel density conversion by performing interpolation processing on the detected radiographic image.
However, depending, for example, on the resolution (resolution) of the radiation detection element and the square grid image one wants to eventually obtain, the pixel information detected by the radiation detection element becomes wasted when the pixel density conversion has been performed. Further, for example, if the resolution after the pixel density conversion is too high compared to the resolution of the radiation detection element, the size of the image data after the conversion increases needlessly and processing speed drops.
The present invention provides a radiation detection element that may prevent an enlargement of the size of image data after pixel density conversion while improving resolution, a method of forming a radiation detection element, a radiographic imaging device using the radiation detection element, a radiographic imaging system, a radiographic imaging method, and a pixel density conversion method.